1. Field of The Invention
Applicant's invention relates to wheelchairs and more particularly to adjustable leg rests for wheelchairs.
2. Background Information
It is well known that the human leg's effective length changes depending on the degree to which the leg is bent at the knee. As the knee is flexed, the overall length of the leg decreases. Conversely, as the knee is extended, the overall length increases.
These facts are reflected in the design of certain wheelchair leg/foot rests--those which may be raised and lowered to achieve much the same effect as that of the leg rest of a recliner. Such leg/foot rests extend in length as they are raised to accommodate the increased length of the user's leg. As the leg/foot rests are lowered to allow the user a standard, upright seating position, the leg/foot rests contract in length.
Currently, the state of the art extendable foot/leg rests employ external pivot arms to effect their extension and contraction. Referring to FIG. 1 of the drawings included herewith, a general representation of a current state of the art foot/leg rest 100 is depicted with the foot/leg rest 100 in the lowered position. Tube 102 attaches to the wheelchair (not shown) in a horizontal orientation. The distal end of tube 102 is formed as a gear member 104. The gear member is rotatably attached to bracket 106. Also rotatably attached to bracket 106 is a second gear 108 which is positioned for engagement with gear member 104. Rigidly attached to gear 104 at its proximal end is a first pivot arm 110. Pivotally attached at its proximal end to the distal end of first pivot arm 110 is a second pivot arm 112. The distal end of the second pivot arm 112 is pivotally attached to tube 114. The distal end of tube 114 exhibits a foot rest 116 against which a user's foot rests. Most often, the foot rest 116 is hingedly attached to tube 114 for allowing the foot rest 116 to be moved for facilitating a user's entering and leaving the wheelchair. The proximal end of tube 114 is telescopically received into tube 118 which is rigidly affixed (by welding) to bracket 106.
From the perspective shown in FIG. 1, the action of the foot/leg rest 100 may be understood as follows: As the lower portion of the foot/leg rest 100 is to be raised (that portion including tubes 118 and 114 and bracket 106), it is moved in a clockwise direction. As bracket 106 moves in relation to the stationary tube 102, the resulting interaction between gears 104 and 108 causes the first pivot arm 110 to likewise move in a clockwise rotation. The resulting interaction respectively between first pivot arm 110 and second pivot arm 112 and second pivot arm 112 and tube 114 causes tube 114 to telescopically extend from tube 118.
As the foot/leg rest 100 is to be lowered, the process is simply reversed with tube 114 telescopically retracting into tube 118.
Difficulties arise from the design of the current state of the art extendable/retractable foot/leg rest. The pivot arms, acting as they do in a scissor-like manner, pose potential safety hazards for users. The pivot arms are also known to snag a user's clothing during use. Finally, the pivot arm assembly is quite weighty and is not particularly attractive from an aesthetic standpoint.